It's been several days now - what's happening with your spot?
It's not syphilis - it appeared way too soon for a syphilis sore, which won't appear until 10 days at the earliest. A syphilis sore is also an open sore, which this isn't.
It sounds more fungal or dermatitis - it's flat and red. The only way to know for sure though is to get a doctor to look at it. Unfortunately, spots and bumps and sores can be caused by so many things that no one can tell you what it is without actually looking at it or testing it.